Electronic ovens



Nov. 1, 1960 D. E. HAHN ELECTRONIC OVENS 2 Sheets-Sheet 1 F iq. 3

Filed Dec. 15, 1958 M m MM,

WWW.

JNVENTOR Donald E. Hahn Nov. 1, 1960 D. E. HAHN ELECTRONIC ovENs 2Sheets-Sheet 2 Filed Dec. 15, 1958 IN V EN TOR Donald E Hahn UnitedStates Patent Ofifice 2,958,754 Patented Nov. 1, 1960 ELECTRONIC OVENSDonald E. Hahn, Chicago, Ill., assignor to General Electric Company, acorporation of New York Filed Dec. 1'5, 1958, Ser. No. 780,430 9 Claims.(Cl. 219-1055) The present invention relates to electronic ovens, andmore particularly to improved window and door constructions for suchovens.

It is a general object of the invention to provide an improved door foran electronic oven which permits viewing of the interior of the oven andprovides a closure which is substantially leak-proof to microwaveradiation.

Another object of the invention is to provide an improved viewing windowfor an electronic oven which permits a high degree of visibility of theoven interior while effectively barring the passage of microwaveradiation.

Still another object of the invention is to provide an improved doorseal for the door of an electronic oven which does not impede theopening and closing of the door while still effecting a seal which issubstantially leak-proof to microwave radiation.

A further object of the invention is to provide an improved electronicoven having various of the features and advantages recited above whilebeing durable, eflicient and economical to manufacture.

In accordance with one embodiment of the invention a viewing window isarranged in the door and has a metallic screen embedded in the glasspane thereof, the metallic screen cooperating with certain portions ofthe door and an improved door seal for providing with the basic ovenshell a cooking chamber which is substantially leak-proof for microwaveradiation. The door may be of the conventional hinged type or it mayform the front panel of a drawer. In either case, a door constructed inaccordance with the preferred embodiment of the invention permitsviewing of the interior of the oven and permits opening and closing ofthe door by application of no more than the conventional opening andclosing force while at the same time effecting a closure of the ovenwhich is substantially leak-proof for microwave radiation. While severalfeatures of thepreferred embodiment of the invention. cooperate toproduce these desired effects, it is to be understood that the variousfeatures are useful individually.

The invention, both as to its organization and method of operation,together with further objects and advantages thereof, will best beunderstood by reference to the following specification, taken inconnection with the accompanying drawings, in which:

Fig. 1- is a front perspective view of an electronic oven embodying thepresent invention;

Fig. 2 is a similar perspective View of the oven but with the door inits opened position;

Fig. 3 is an elevational view, partially in cross section, illustratingthe general arrangement of the oven, the source of microwave radiationand the interconnecting wave guide;

Fig. 4 is a cross-sectional view of the front portion of the oven, takenin the direction of the arrows along the line 4+4 in Fig. 1;

Figs. 4A and 4B are partial cross-sectional views showing" the left andright hand ends, respectively, of the front portion of the oven, as inFig. 4, except showing the door slightly ajar;

Fig. 5 is a partial cross-sectional view of a viewing window of theoven, taken in the direction of the arrows along the line 55 of Fig. 4;

Fig. 6 is a partial cross-sectional view similar to Fig. 5 butillustrating another embodiment of the invention; and,

Fig. 7 is a partial cross-sectional view similar to Fig. 4A, butillustrating a different embodiment of the invention.

Referring now to Figs. 1 to 3, inclusive, of the drawings, theelectronic oven there illustrated, and embodying the features of thepresent invention, comprises an oven chamber 10 defined by electricalconductive walls, and particularly by a metallic shell 11 and a metallicdoor 12. In Fig. 3, a magnetron 13 is schematically illustrated, and isshown connected to the oven chamber 10 by a suitable wave guide 14. Themagnetron 13 which serves as a source of microwave energy for the ovenchamber 10 is of conventional form and may have an operating frequencyof 2450 megacycles; and likewise the wave guide 14 may be ofconventional construction and arrangement. Also, in passing, it is notedthat the dimension of the oven chamber 10 in each direction (height,width and depth) is substantially greater than the wave length of themicrowave energy supplied thereto from the magnetron 13; wherebycentimeter standing waves are provided in the oven chamber 10.

As will be apparent by reference to Figs. 1 and 2, the door 12 of theillustrated embodiment of the invention is hinged. However, as willsubsequently become apparent, the various features of the presentinvention are equally applicable to a door which constitutes the frontpanel of a drawer. In either case, it is, of course, desired that theoven shell 11 be of metal and form a continuous, closed box except forthe duct opening and the door opening, and that the door effectivelyclose the latter opening against leakage of microwave radiation when thedoor is in its closed position. At the same time, it is desired that aviewing window be provided, preferably in the door, and that the sealbetween the door 12 and the oven shell 11 require no special fasteningor manipulation, whereby the door may be opened and closed with theapplication of nothing more than conventional opening and closingforces.

Referring now to Figs. 4, 4A and 4B, it will be seen that the oven shell11 turns outwardly at the mouth of the oven to form a flange 15 againstwhich the door closes. The flange 15 preferably extends entirely aroundthe mouth of the oven and constitutes a continuation of the metallicshell 11, being either integral therewith or connected thereto such thatthe shell 11 and the flange 15 form a continuous metallic wall. Beyondthe flange 15, the metallic sheet may be arranged as shown to provide arecess for the door 12 and to enclose heat insulating material 16.

The door 12 includes a basic construction comprising an outer wall 21,an inner wall 22 and enclosed heat insulating material 23. This portionof the door may be of conventional construction and in accordance withthe embodiment of the invention illustrated in Fig. 4 need not be reliedupon to bar the passage of microwave radiation from the oven to thesurrounding space. In accordance with this embodiment of the invention,a metal sheet 25, preferably of stainless steel, is arranged on the door12 and serves as a barrier to passage of microwave radiation. It is tobe understood, however, that the metal sheet 25 may, in part, compriseor be replaced by the inner wall 22 of the door 12 without departingfrom the spirit of the invention.

Near the periphery of the door the metal sheet 25 overlies'a resilientpad 26 which extends entirely around the mouth of the oven and ispreferably formed of polyurethane foam, this material having the desiredflexibility and resilience and being capable of withstanding the ovenheat. Immediately opposite the pad 26 and mounted on the flange 15 is ametallic gasket 27 which also extends entirely around the mouth of theoven and projects outwardly from the flange 15. This annular member ismetallic in order to reflect microwave radiation and is secured to theflange 15 in such a manner as to provide therewith an unbroken metallicwall, to the effect that microwave radiation may not pass therebetween.

Arranged immediately beyond the edge of the metal sheet 25 is an annularmember 28 which is secured to the door 12 and which extends entirelyaround the outer edge of the metal sheet 25 and the mouth of the oven.This annular member 28 extends from the door 12 toward the flange 15 andhas a free edge projecting toward the center of the door and overlyingthe edges of the sheet 25 such that the edges of the metal sheet arecon- 'cealed. Still further, this member has a re-entrant lip, wherebythe edge of this member is also substantially concealed, all as shown inFigs. 4 and 4A.

When the door 12 is in its fully closed position, as illustrated in Fig.4, the annular member 28 engages the flange 15. However, prior to thedoor reaching its fully closed position, and when the annular member 28is spaced a short distance from the flange 15, the gasket 27 makesengagement with the metal sheet 25. Further closing movement of the doorcauses compression of the pad 26 and yielding of the sheet 25 from thecondition illustrated in Fig. 4A to the condition illustrated in Fig. 4.The sheet 25 is preferably thin (of the order of .010" thick) in orderto facilitate the required bending or yielding thereof. Such compressionof the pad 26 and yielding of the sheet 25 permit this further closingmovement of the door such that the annular member 28 may be brought intoengagement with the flange 15.

In Fig. 4 it may be seen that a double seal is thus elfected at thejuncture of the door and the oven shell. More particularly, a first sealcomprises the gasket 27 and the metal sheet 25. A tight seal is obtainedbetween these parts by virtue of the resilience of the pad 26 and thesheet 25. A second seal is effected between the flange 15 and theannular member 28. Preferably, the annular member 28 is resilient andsomewhat flexible in order that it may make good contact with the flange15.

It should be noted further that any microwave radiation which might passbetween the gasket 27 and the metal sheet 25 does not have direct accessto the joint between the annular member 28 and the flange 15, butinstead would tend to be trapped by the annular member 28. Attention isfurther directed to the fact that this double seal requires nomanipulation of parts by the operator and requires no more than theconventional opening and closing forces. In order that the resilient pad26 may be compressed during the final closing movement of the door 12 toassure engagement of the annular member 28 with the flange 15, it isdesirable that the door 12 be biased toward closed position by a smallforce. It is conventional, however, in oven construction to provide theoven door with a significant closing bias. Where the oven door is hingedit is usually biased in a closing direction during the final closingmovement by weights or springs. Where the oven door is in the form ofthe front panel of a drawer, it is conventionally biased toward closedposition during the final portion of the closing movement by gravity.Such closing bias is desirable since it eliminates the necessity of adoor latch, all as is well understood and conventional in the art.Conventional door closing bias is suflicient to provide compression ofthe resilient pad 26 and assure engagement of the annular member 28 withthe flange 15. If desired, the metal sheet 25 may extend uninterruptedover the mouth of the oven and, more particularly, over the area definedby the resilient pad 26 or the gasket 27.

In the illustrated embodiment of the invention, however, a viewingwindow 30 is provided through which the operator may view the interiorof the oven. It is necessary, of course, that the window 30 efiectivelybar the passage of microwave radiation and that it be connected directlyor indirectly with the metal sheet 25 to effect a continuous barrier tothe passage of microwave radiation.

In the embodiment of the invention illustrated in Fig. 4 the window 30'comprises two panes which may be identical, two panes being provided inorder to minimize the escape of microwave radiation. The construction ofthese panes is best illustrated in Fig. 5. It will there be seen thatthe pane is laminar in construction, including two sheets 31 ofheat-resistant glass and an inner lamination 32 of any suitable materialsuch as a thermoplastic or thermosetting resin or other suitable plasticmaterial. it is necessary, of course, that the material of which thisinner lamination is composed be capable of withstanding oven heatwithout detrimental effect. Since laminated glass is well-known in theart, the specification of particular materials is unnecessary in thepresent application.

Embedded within the inner lamination 32 is an aluminum wire screen 33which is preferably of at least 12 to 13 mesh. It is preferred, also,that the side of the screen 33 facing outwardly of the oven be blackenedfor improved visibility of the interior of the oven. As will be obviousto those skilled in the art, such blackening of the aluminum wire screenmay be accomplished by various processes which would result in oxidizingor sulphurizing the surface of the aluminum wire. Blackening of theouter side of the screen greatly reduces the reflection of outside lightand thereby improves visibility of the interior of the oven from theoutside.

It has been found that a relatively fine screen having approximatelyopenings per square inch and providing approximately 50% clear openingpermits good visibility of the interior of the oven under normalconditions when a double pane is employed, as shown in Fig. 4. It hasbeen found also that a double pane employing such a screen bars thepassage of microwave radiation to such an extent that the leakage fallssubstantially below the maximum specified by the Federal CommunicationsCommission.

It has also been found that with the screen having a given percentage ofclear space the fineness of the screen has relatively little effect onradiation leakage. However, a relatively fine screen, such as thesuggested screen having 150 openings per square inch provides improvedvisibility over a relatively coarse screen. For this reason, it isrecommended that the screen be at least 12 to 13 mesh.

As is best seen in Fig. 4, the wire screens 33 are made to extend beyondthe edge of at least one of the glass sheets 31 of the associated panein order that they may be engaged by a U-shaped member 35which extendsentirely around the window 30. Preferably, the inner or facing sheets 31of the two panes extend beyond the outer sheets thereof and are spacedapart by another U-shaped member 36 which also may extend entirelyaround the peripheral portion of the window 30. An annular plate 37 alsoextends entirely around the window 30 and is clamped to the body of thedoor 12 as by screws 38. The plate 37 is preferably welded to, orintegral with, the U-shaped member 35 and overlies the inner edge of themetal sheet 25 as shown.

With this arrangement the window 30 is brought into effective engagementwith the metal sheet 25 to complete the closure of the oven againstleakage of microwave radiation. More particularly, the oven shell 11,the metal gasket 27, the metal sheet 25 and the window 30 form acontinuous and efiective barrier against the leakage of microwaveradiation. The only openable joint in this barrier is that between themetal gasket 27 and the metal sheet 25, and this joint is backed up by asecond seal, namely the seal between the annular member 28 and theflange 15, which is staggered or out of alignment with the first seal.It should be noted further that the entire radiation barrier is in firmelectrical contact whereby any induced currents in any part of theradiation barrier may readily be grounded by a single ground connection.

An alternative embodiment of the viewing window is illustrated in Fig.6. Here the window 30 consists of three sheets 31' of glass with twointermediate laminations 32 of plastic material and two embedded wirescreens 33'. With this arrangement only a single pane is required, thissingle pane having two wire screens and therefor having the sameeffectiveness as a radiation barrier as the double pane of Fig. 4. Withthe window construction of Fig. 6 the central glass sheet and the twowire screens preferably extend beyond the two outer glass sheets, andthe two screens are engaged by a U-shaped member 35 which preferablyextends entirely around the periphery of the window 30'.

For the purpose of illuminating the oven chamber 10, an electric lamp 50is arranged in a reflector 51 disposed in the space between the innershell or liner 11 and the outer wall of the oven 10 and embedded in thesurrounding heat insulation 52 disposed therebetween. More particularly,the reflector 51 communicates with an opening 53 provided in theadjacent portion of the liner 11, which opening 53 is suitably closed bya removable window 60 accommodating the ready passage of light from theelectric lamp 50 into the oven chamber 10. Preferably the window 60 isalso of the construction and arrangement of the viewing window 30 thatis incorporated in the door 12, and as previously described. Thisarrangement of the window 60 prevents the microwave energy in the ovenchamber 10 from entering the reflector 51, so as to eliminate thepossible induction of parasitic microwave electric currents in thecomponents of the electric lamp 50.

:It may now be seen that the metal sheet 25 need not necessarily extendfrom the pad 26 and the gasket 27 to the edge of the window 30. If theinner wall 22 of the door 12 is of metal, a metal sheet 25 of relativelynarrow annular construction may be employed as illustrated in Fig. 7.Its outer edge portion overlies the pad 26 and its inner edge portion issecured to the inner wall 22 of the door as by screws 39. In this casethe inner wall 22 of the door serves as the primary radiation barrierextending outwardly of the oven door window, if a window is employed,and the metal sheet 25' serves merely as a flexible continuation thereofto cover the flexible pad 26 and to make contact with the metal gasket27. In other words, the inner wall of the door and the narrow annularsheet 25' serve, together, as the metallic sheet 25 of the embodimentshown in Fig. 4.

An electronic oven has now been disclosed having an improved door sealand an improved, cooperating viewing window. These two features of theinvention permit a readily openable door and a viewing window whichsubstantially eliminate leakage of microwave radiation. It will beapparent that the door seal and the viewing Window have utility separateof each other, if desired. The door seal may for example be used with adoor having no viewing window, and the improved viewing window may beemployed separately of the improved door seal and may be used on a fixedwall of an elec tronic oven.

Various modifications of the disclosed embodiments of the invention willbe apparent which fall within the spirit of the invention. For example,the gasket 27 may, if desired, be integral with the flange or the shell'11 or both, in which case it continues to form and serve as a gasket.

Accordingly, While there has been described what are at presentconsidered to be the preferred embodiments of the invention, it will beunderstood that various 6 modifications may be made therein, and it isintended to cover in the appended claims all such modifications as fallwithin the true spirit and scope of the invention.

What is claimed is:

1. An electronic oven comprising a metallic shell defining an ovencavity adapted to be supplied with microwave energy, said shell havingan opening therein for providing access to said oven cavity andincluding an outwardly facing flange defining said opening, a door forclosing said opening, a metallic gasket surrounding said opening andprojecting outwardly from said flange, a continuous resilient padarranged on the inner side of said door to face said gasket when saiddoor is in closed position, a metallic sheet on the inner side of saiddoor overlying said pad and extending toward the center of said door, anannular metallic member secured to said door and projecting toward saidflange, said gasket being engageable with said metallic sheet as saiddoor closely approaches its closed position, said pad being compressibleto permit further door closing movement whereby said annular member mayengage said flange outside and closely adjacent to said gasket, and aviewing window in said door, said window comprising a pane ofheat-resistant glass with a wire screen embedded therein, said wirescreen being exposed at the edges of said pane, and said metallic sheetextending to and engaging the edges of said screen.

2. An electronic oven comprising a metallic shell defining an ovencavity adapted to be supplied with microwave energy, said shell havingan opening therein for providing access to said oven cavity andincluding an outwardly facing flange defining said opening, a door forclosing said opening, a metallic gasket surrounding said opening andprojecting outwardly from said flange, a continuous resilient padarranged on said door to face said gasket when said door is in closedposition, a metallic sheet on the inner side of said door overlying saidpad and extending toward the center of said door, an annular metallicmember secured to said door and projecting toward said flange and havinga free edge projecting toward the center of said door to overlie theedges of said sheet, said gasket being engageable with said metallicsheet as said door closely approaches its closed position, said padbeing compressible to permit further door closing movement whereby saidannular member may engage said flange outside and closely adjacent tosaid gasket, and a viewing window in said door, said window comprisinginner outer facing panes each comprising a pane of heat-resistant glasswith a wire screen embedded therein, said Wire screens being exposed atthe edges of said panes, and said metallic sheet extending to andengaging the edges of said screens,

3. In an electronic oven comprising a metallic shell defining an ovencavity adapted to be supplied with microwave energy, said shell havingan opening therein for providing access to said oven cavity andincluding an outwardly facing flange connected to said shell anddefining said opening, a door for closing said opening, a metallicgasket surrounding said opening and projecting outwardly from saidflange, a continuous resilient pad arranged on said door to face saidgasket when said door is in closed position, a metallic sheet on theinner side of said door overlying said pad and extending toward thecenter of said door, an annular metallic member secured to said door andprojecting toward said flange, said gasket being engageable with saidmetallic sheet as said door closely approaches its closed position, saidpad being compressible to permit further door closing movement wherebysaid annular member may engage said flange outside and closel adjacentto said gasket, and a viewing window in said door, said windowcomprising a pane of heat-resistant glass with a wire screen embeddedtherein, said wire screen being exposed at the edges of said pane, andsaid metallic sheet extending to and engaging the edges of said screen.

4. An electronic oven comprisinga metallic shell defining an oven cavityadapted to be supplied with micromave energy, said shell having anopening thereinto affording access to said oven cavity and including anoutwardly facing boundary flange surrounding said opening, a door forclosing said opening, a metallic boundary gasket carried by said shelland surrounding said opening and projecting outwardly from said boundaryflange, a compressible boundary pad carried by the inner side of saiddoor and facing said boundary gasket when said door is in its closedposition, a resilient metallic boundary member carried by the inner sideof said door in surrounding relation with respect to said boundary pad,and a flexible metallic sheet carried by the inner side of said door andoverlying said boundary pad and extending toward the center of saiddoor, said boundary gasket engaging and flexing said metallic sheet assaid door closely approaches its closed position and said boundary padbeing compressed by the flexing of said metallic sheet to permit furtherclosing movement of said door, said boundary member engaging saidboundary flange outside of and closely adjacent to said boundary gasketand being deformed into fitting relation with said boundary flange whensaid door is in its closed position.

5. The electronic oven set forth in claim 4, wherein said door includesa metallic inner wall, said boundary pad is carried by the boundaryportion of said inner wall, the outer portion of said metallic sheetoverlies said boundary pad, and the inner portion of said metallic sheetis secured to the central portion of said inner wall.

6. The electronic oven set forth in claim 4, wherein said boundarymember has boundary edges projecting toward the center of said door andoverlying the boundary edges of said metallic sheet, the boundary edgesof said metallic sheet being flexed by engagement with said boundarygasket from normal engagement with the boundary edges of said boundarymember.

7. An electronic oven comprising metallic walls defining an oven cavityadapted to be supplied with microwave energy, one of said walls havingan opening therein, a metallic frame carried by and electricallyconnected to said one wall and arranged in said opening about theboundary thereof and defining a window accommodating viewing from theexterior of the interior of said oven cavity, and a pane supported bysaid frame and closing said window, said pane including a body ofheat-resistant transparent glass and a metallic screen embedded therein,the boundary edges of said screen being electrically connected to saidframe, said screen being of a mesh effective to preclude escape ofmicrowave energy from said cavity through said Window withoutsubstantial interference with viewing through said pane.

8. An electronic oven comprising metallic walls defining an oven cavityadapted to be supplied with microwave energy, one of said walls havingan opening therein, a metallic frame carried by and electricallyconnected to said one wall and arranged in said opening about theboundary thereof and defining a window accommodating viewing from theexterior of the interior of said oven cavity, and a pane supported bysaid frame and closing said window, said pane being of sandwichstructure including outer sheets ofheat-resistant transparent glass andan inner layer of heat-resistant transparent plastic material and ametallic screen embedded in said inner layer, the boundary edges of saidscreen being electrically connected to said frame, said screen being ofa mesh effective to preclude escape of microwave energy from said cavitythrough said window without substantial interference with viewingthrough said pane.

9. The electronic oven set forth in claim 8, wherein said screen is ofat least 12 mesh.

References Cited in the file of this patent UNITED STATES PATENTS2,748,239 Long et al. May 29, 1956 2,831,952 Warner Apr. 22, 19582,920,174 Haagensen J an. 5, 1960

